“Think twice before putting your hands on T staff. We will find you, arrest you, and prosecute you,” Transit Police Chief Paul MacMillan says in a ­recorded public service announce­ment that will soon be heard in all T stations.

“Your safety is our top priority,” MBTA general manager Beverly Scott says in the recording. “Please do your part to ­ensure the safety of our operators and T customers.”

The T will also hang signs in buses that show two arms in handcuffs and a message saying “Don’t touch the driver.”

During the first four months of 2012, 24 assaults on MBTA employees were reported. During the first four months of 2013, there were 28 reported assaults.

In one particularly alarming case in March, 15 to 20 teenagers punched an MBTA bus driver and tried to pull him from the driver’s side window while the bus was picking up passengers in Dorchester, authorities said. Two suspects have been arrested.

‘We must proactively inform our customers that an assault on a T employee is against the law.’

Scott cited that case in a letter to T employees in April. She said the driver was recovering and that there had been an outpouring of support from the public wishing the driver well and offering help in identifying the perpetrators.

“But this incident reminds us that we must proactively ­inform our customers that an assault on a T employee is against the law, and that ­offenders will be prosecuted,” Scott wrote. “Front-line MBTA employees are particularly vulnerable to such attacks.”

Her letter said T management and the employee union are committed to collaborating to solve the problem.

As part of that effort, the T plans to add surveillance cameras inside buses; expand ­employee training on how to de-escalate potentially violent situations and how to protect themselves; and assess whether to install partitions to separate drivers from passengers.

“Dr. Scott is determined to reverse this ugly trend,” T spokesman Joe Pesaturo said in an e-mail Monday.

Scott vowed to continue to push for state legislation that would “strengthen the law for assaulting an operator.”

“I want you to know . . . that we will not sit by idly and let these egregious acts go un­answered,” Scott wrote. “Certainly, getting assaulted is not part of any T employee’s job.”